Description of Model Project Work
Nature has evolved a variety of strategies to utilize O2 for the controlled oxidation of organic molecules The formal incorporation of an oxygen atom into unactivated C-H bonds typically requires the use of transition metal centers in either the reduction of dioxygen and/or in the formation of the reactive intermediate responsible for the oxidation reaction. The initial steps of dioxygen activation involve the formal two-electron reduction of O2 that is necessary to generate the more reactive peroxy moiety. There are numerous mechanisms by which the enzymatic reduction of dioxygen can proceed; all of which share a fundamental mechanistic feature, namely the generation of a high valent reactive iron species following heterolytic cleavage of a coordinated peroxide ligand. Iron-based monooxygenases appear to have characteristics that suppress homolytic cleavage of bound hydroperoxide groups. If allowed to occur, homolytic O-O bond scission would generate hydroxyl radicals that, while powerful oxidants in their own right, cannot be easily controlled and thus are not useful for performing selective oxidation reactions with high efficiencies in enzyme active sites. Despite significant advances in our understanding of the structural, spectroscopic, and mechanistic issues of iron-based enzymatic alkane and arene oxidation processes, the development of synthetic analog systems that parallel key steps in the biological oxidation of hydrocarbons remains a major challenge. The development of systems that are capable of oxidizing hydrocarbons via the same pathway exhibited in the parent enzymes, will provide greater insights into both the intrinsic reactivity of non-heme iron centers, as well as the characteristics of the reactive intermediate(s) can be obtained.

The Caradonna laboratory has developed a class of binuclear non-heme ferrous complexes that are capable of catalyzing the oxidation of alkanes in the presence of either oxygen atom donor (OAD) molecules or alkyl hydroperoxides. Our approach uses a combination of synthetic, mechanistic, and spectroscopic methods to investigate the catalytic chemistry of complexes that are designed based on principles obtained from metalloenzyme studies. We focus on two fundamentally different, although related aspects of alkane oxidation:

  • Development of a molecular-level understanding of the mechanism by which binuclear ferrous compounds catalyze the oxidation of alkanes and arenes, and
  • Exploration of the chemical nature and electronic characteristics of the iron-based reactive intermediate(s) responsible for the formal transfer of an oxygen atom to an alkane substrate